Parse optional account_ids in run handler

internal/httpapi/run_test.go

@@ -26,3 +26,25 @@ func TestImportCSVFailsOnBadEncKey(t *testing.T) {
 		t.Fatalf("import must fail on bad EncKey, got %d", rw.Code)
 	}
 }
+
+func TestParseRunAccountIDs(t *testing.T) {
+	// empty body => nil (run all)
+	req := httptest.NewRequest("POST", "/api/tasks/1/run", strings.NewReader(""))
+	ids, err := parseRunAccountIDs(req)
+	if err != nil || ids != nil {
+		t.Fatalf("empty body must yield nil ids, got %v err=%v", ids, err)
+	}
+
+	// explicit selection
+	req = httptest.NewRequest("POST", "/api/tasks/1/run", strings.NewReader(`{"account_ids":[3,7]}`))
+	ids, err = parseRunAccountIDs(req)
+	if err != nil || len(ids) != 2 || ids[0] != 3 || ids[1] != 7 {
+		t.Fatalf("must parse account_ids, got %v err=%v", ids, err)
+	}
+
+	// malformed JSON => error
+	req = httptest.NewRequest("POST", "/api/tasks/1/run", strings.NewReader(`{bad`))
+	if _, err := parseRunAccountIDs(req); err == nil {
+		t.Fatal("malformed body must error")
+	}
+}